Help with duplicate emails being sent.

Recently, my Outlook Express on a Vista Laptop is sending two copies of every email I send. What do I need to change to stop this from happening?

Thanks.

 

Are you using Norton? This can be a cause of duplicate emails.

 

No. I am using Trend Micro's anti-virus.

 

My Dad has this happening with his Outlook Express e-mail as well. Whenever he sends me an e-mail that includes an attachment, (for example: a photo) it gets sent to me twice. Text messages are fine.

We both use AVG and ZoneAlarm.
We both have XP Home.
We both have Sympatico Internet Service.

I was receiving duplicates when he lived at his old house while on High Speed, and now again at his new house in another city, only this time he's on Dial Up (as that's the only service offered). I'm still on the same High Speed connection, no duplicates from any one else, just from him.

Sorry to hijack your thread, but I'm curious as well.